The Best Way to Check Transmission Fluid

The Best Way to Check Transmission Fluid
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You’re not going anywhere if your car’s engine is toast, and the same goes for the transmission. This case containing gears, clutches, electrical parts and fluid is more intricate and much less understood than an engine, and few DIYers will try a repair themselves. Keeping it healthy is key, which is why it’s important to know how to check transmission fluid.

Avoid potentially costly and frustrating repairs by maintaining your transmission according to the carmaker’s recommendations and standards. That begins with inspecting the fluid. Here’s what you need to know including the best way to check transmission oil and what to do if it’s low.

How to check transmission fluid

Most drivers know how to check the engine oil level and condition, and it’s very similar for most cars to check the transmission fluid. There are a few exceptions that you’ll need to watch for as well.

Park the car on a level surface

Find a flat, level surface to park your car and set the parking brake. A garage or parking lot works well. The fluid in a transmission likely won’t read accurately if your car isn’t on a flat area, much like tilting a half-full water glass makes it look higher on one side and lower on the other.

Start the engine

If the engine is off, fire it up. For most vehicles, the fluid needs to circulate to fill all the small voids in the transmission to get an accurate reading, and the fluid also expands as it heats up. If you check the fluid when it’s cold and might’ve drained back into the pan, your reading won’t be as spot on as it could be.

If you’re unsure if your engine should be running or not, check the dipstick. It’s often stamped into the flexible metal, or the owner’s manual will have that info too.

Locate the dipstick

The best way to check transmission fluid is with the dipstick that comes with the vehicle. Under the hood, look for a handle or finger loop to pull out located on the opposite side of the engine from the belts. It might have an image of a gear on it, and it could be black, orange or red.

Sometimes it’s tough to see, nestled between hoses or ducts in the engine bay. Generally, a rear-wheel-drive or four-wheel-drive vehicle will have its dipstick near the firewall, while front-wheel-drive and all-wheel-drive vehicles will have it on the driver’s side closer to the front.

Check the transmission fluid

Next, with a shop towel or rag in hand, pull the dipstick out of the tube. Be careful not to fling droplets. Your first action is to wipe off the dipstick and reinsert it into the tube. Likely, there’s fluid that’s splashed onto the dipstick from when it was running or driving previously, which can create a false reading. Then, pull it out again.

With the dipstick out, identify where the fluid reaches. Look for hash marks, lines or words to indicate the level. It might say “FULL” and “ADD”, or it could be stamped with “COLD” and “HOT.” This is the range of where the fluid should be when you check it.

Along with the level, check the condition. If the fluid is bright pink or red, light honey brown, blue, or pale yellow, that’s a good sign. Of course, the fluid color depends on the type of car you drive. If the color is more of a deep brown or black, or if the fluid smells pungent and burnt, it’s time to change it. If it looks like strawberry milkshake, that indicates water in the transmission and could mean a major repair is necessary.

What to do if your transmission fluid is low

If the fluid is lower than the markings on the dipstick, add fluid. Transmission fluid is a synthetic fluid with additives chosen by manufacturers to protect their parts, so choosing the right type is crucial. Find the spec in a few different places: on the dipstick, in your owner’s manual or maintenance guide and on your carmaker’s website.

However, low fluid isn’t a normal condition, so there could be a leak somewhere that needs your attention.

Signs of low transmission fluid

The transmission has several places where a leak could spring up, including an input shaft seal, output shaft seal, oil pan gasket, and transmission oil cooler hoses. It could be any of these items that has sprung a leak or even a punctured trans oil cooler that’s incorporated into the radiator.

When the fluid drops enough, you’ll begin to experience symptoms that could include:

  • Oily stains on the garage floor or driveway
  • A delay engaging into drive or reverse
  • Shift flares or harsh clunks when the transmission is changing gears
  • Quick fluid breakdown due to higher temperatures
  • A Check Engine Light with transmission-related DTCs
  • Dropping out of gear while you drive
  • Grinding, clunking, whining or whirring noises while you drive

How often to check transmission fluid

Now that you know how, check your transmission fluid regularly to avoid problems. Some experts recommend checking the fluid monthly, but that’s not always realistic. At the minimum, your transmission fluid should be checked for condition and level at every oil change interval.

The consequences of a leak you’re unaware of can be drastic, especially if it’s not caught before symptoms appear. Once the signs of low fluid show up, it could be too late and a repair is necessary.

Conclusion

You know how important it is to have oil in your engine, and the same is true for your transmission. At $10 or so per quart, it’s much cheaper to top up low transmission fluid than to spend thousands to rebuild or replace your transmission. Check it monthly if possible and watch for signs that it’s low while you drive.

Frequently Asked Questions

What happens if you drive with low transmission fluid?

Low transmission fluid will become evident with symptoms like slow or sloppy shifts, warning lights and burnt fluid. If you keep driving with low fluid, you risk causing major damage that requires costly repairs.

Will the engine light come on if transmission fluid is low?

The Check Engine Light might illuminate with low transmission fluid on certain models by triggering a low pressure code like P0868. However, it doesn't apply to all vehicles and shouldn’t be relied on to monitor for low fluid.

Do you check the transmission fluid with the engine running?

Yes, running the engine circulates and warms the transmission fluid so you get the most accurate reading possible.


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Disclaimer: The above is solely intended for informational purposes and in no way constitutes legal advice or specific recommendations.